1. Technical Field
This invention relates to an image processing art for forming an image in color reproduction roughly equivalent to an original image on a second image output device with using the original image created for the purpose of being output on a first image output device.
2. Related Art
At present, various types of color-devices such as a digital camera, a color scanner, a color printer, and a color display become prevalent and are used widely, and the market requirements for color are also considerably high. Particularly in a system used in DTP (desktop publishing), etc., the requirements for color are considerably high and CMS (color management system) in each device is indispensable. A print simulation color proofreading art of simulating printed color in printing on a printer for check using the CMS technology is becoming pervasive.
A paper white (ground color) reproducing art is an important art for print simulation. Various paper types exist as paper used in print, and the paper white reproducing art is an art of reproducing white color of paper. At present, the paper white reproducing art is roughly classified into three methods of relative conversion, reproduction of only absolute white, and absolute reproduction.
The relative conversion is an art of reproducing paper white of a printing machine with using paper white of a printer and is a method of shifting the whole colors together with the white. The feature of this art is that since the paper white of the printing machine is matched with the paper white of printer, even if the paper white of the printer is whiter than that of the printing machine, color cast over the whole printer output can be suppressed. Also, since other colors are also shifted as a whole along with the shift of the paper white, print simulation can be executed with the collective impression received from the output image being maintained. As a shortcoming, however, it is difficult to perform absolute color reproduction of the print colors. Thus, if the paper white of the printing machine and the paper white of the printer are largely different, a problem may arise in color reproduction because of the whole color shift.
The reproduction of only absolute white is to shift the paper white of a printing machine to the paper white of a printer as in the relative conversion. However, the reproduction of only absolute white keeps absolute color reproduction for colors other than the paper white so that the other colors of the printing chine is reproduced on the printer. In so doing, color cast at the time when the printer outputs can be suppressed as with the relative conversion. Also, the other colors are converted so that the other colors are matched the resultant colors in terms of absolute color measurement. Therefore, a serious problem does not arise in color reproduction as print simulation. As a shortcoming, however, tone jump in the vicinity of a white or the like is named as a problem since only white of the printing machine is shifted to white of the printer.
The absolute reproduction is a reproduction method of matching colors of a printing machine and those of the printer with each other in terms of color measurement. The color of paper white of the printing machine is also reproduced faithfully so that the paper white of the printing machine is matched with that of the printer in terms of color measurement match. Accordingly, color measurement match of the print completion state in print can be conducted and simulation in a state closer to the print completion can be conducted. As a shortcoming, however, absolute match is conducted for the paper white. Thus, color cast is found if the color reproduction of the printer is observed.
Thus, the respective paper white reproduction arts have the merits and the demerits, and any of the reproduction arts is selected in accordance with purpose and the feature of each color reproduction. An art with higher color reproduction accuracy is required in the use of the print simulation as described above. Thus, the absolute reproduction is often selected. However, color cast, which colors on the whole paper plane as described above, occurs even when print simulation is executed. Thus, an art of lessening the color cast and providing high color reproduction accuracy is demanded.
Color gamut compression processing is executed to convert such a color outside the color reproduction area into a reproducible color. However, there is a possibility that this processing causes gradation compression or significant color difference may occur.